Prerefining blast furnace iron



Sept 6, 1956 F. x. TARTARON 3,271,128

PREREFINING BLAST FURNACE IRON Filed July 9, 1963 INVENTOR FHA/V675 X. TARTARON W BY A'ITORNEYS United States Patent 3,271,128 PREREFINING BLAST FURNACE IRON Francis X. Tartaron, Pittsburgh, Pa., assignor to the United States of America as represented by the Secretary of the Interior Filed July 9, 1963, Ser. No. 293,913 4 Claims. (Cl. 7560) The invention herein described and claimed may be manufactured and used by or for the Government of the United States of America for governmental purposes without the payment of royalties thereon or therefor.

This invention is concerned with prerefining of molten iron by reaction with an oxidizing gas.

The figure shows a vertical section of the apparatus employed in the process of the invention.

The current preponderant tonnage of steel is produced by the open-hearth furnace in which impurities such as silicon, phophorus and carbon are removed from blast furnace iron by means of a gaseous oxidation process. This process, however, is slow and costly, requiring heavy and expensive equipment. It is also plagued by fluctuations in chemical content of the materials processed.

It is accordingly an object of the present invention to speed up the open-hearth process.

It is a further object of the invention to eliminate or substantially decrease the fluctuations in chemical content of the iron to be processed in the open-hearth furnace.

A still further object of the invention is that of reduction of the quantity of slag produced in the open-hearth furnace in order to speed transfer of heat from flame to metal.

It has now been found that these objectives may be accomplished by means of a prerefining process in which molten iron from the blast furnace is passed through a funnel-shaped vessel, in which the molten iron is subjected to the action of an oxidizing gas. This gas oxidizes the silicon dissolved in the iron to silicon dioxide which separates as a slag layer that floats on top of the liquid iron.

The invention will be best described by reference to the figure. Molten iron is directed from feed pipe 1, through spout 2 into the top of funnel-shaped vessel 3. Spout 2 is positioned so as to direct the flow of molten iron horizontally and tangential to the inner surface of the cone-shaped portion 3a of vessel 3. The metal follows a spiral path down the inner surface of cone-shaped portion 3a and discharges at the bottom of vessel 3 through outlet 8. Friction between the molten iron and the vessel surface produces internal currents in the liquid. The over-all effect is that of a rotating liquid with internal currents bringing new metal to the surface.

A stream of oxidizing gas is directed onto the surface of the molten metal by means of gas feeding device 4. The apparatus of the figure, used in the examples, is also provided with drainage valve 5, control valve 6 and cover 7. The drainage valve was opened at the end of a run to drain off iron or slag that did not enter the spout 2. The control valve was used to decrease the quantity of oxygen that flowed down through the exit of the cone. The cover was used to prevent escape of oxygen from the upper portion of the cone. The drainage valve, control valve and cover were included to obtain optimum results with the materials and conditions of the examples; none is an essential part of the invention. They may be made of any suitable refractory material.

Examples 1-4 In these examples molten iron, immediately after tapping from the blast furnace, was poured from the ladle into feed pipe 1 as fast as possible so as to fill the feed pipe. Filling the feed pipe produces maximum pressure 3,271,128 Patented Sept. 6, 1966 at spout 2 and thus gives maximum velocity of discharge at the spout. Simultaneously with pouring of the iron, oxygen was introduced through feeding device 4. Pouring time was about 4 minutes. The product was discharged into a ladle and when the slag layer was removed the desiliconized iron was ready for final treatment in the open hearth furnace. Results are given in Table 1.

TABLE 1 Weight of Silicon Silicon Silicon Run No. iron in feed, in proremoved,

treated, lb. pct. duct, pct. pet.

Effectiveness of the process in removal of silicon from the molten iron is apparent from the data of the table.

The examples are given for purposes of illustration only. As will be apparent to those skilled in the art, many modifications may be made in the process without departing from the essential spirit and scope of the invention. Any method of bringing feed from the blast furnace to the funnel-shaped vessel can be employed, e.g., when the blast furnace is tapped, the molten iron could be directed immediately into the vessel without use of a ladle or feed pipe.

The vortex cone need not be enclosed if no danger of contamination exists. Also, the oxidizing gas can be blown down into the molten iron employing a lance.

Though oxygen gas is generally most efficient in oxidizing the silicon, other oxidizing gases such as air and enriched air may be used. Furthermore, the gas may contain suspended solids such as fine iron oxides, lime or other solids to effect various reactions with the iron.

The exact shape of the funnel-shaped vessel is also not critical, provided it is generally cone-shaped so as to provide the necessary vortex motion of the molten iron. The vessel of the examples was made of carbon steel lined with refractory brick; however, it may be made of any conventional material having suitable strength and refractory properties. The feed pipe is constructed of similar materials.

The exact nature of the gas feeding device may also be varied to provide maximum contact between the molten iron and the oxidizing gas for a given set of operational variables, i.e., type and velocity of molten iron, size of the apparatus and volume of molten iron, etc. In the examples the device was a simple pipe with holes drilled in the short section.

The spout through which the molten iron is directed into the funnel-shaped vessel may also be varied for maximum efficiency, e.g., it may terminate in a nozzle designed to achieve optimum distribution of the molten metal in the cone.

The process is applicable to removal of impurities in blast furnace iron other than silicon. Blast furnace iron contains sulfur, carbon and phosphorus in addition to silicon. These elements may also be removed by the process of the invention.

What is claimed is:

1. A process for prerefining molten iron comprising:

(a) passing a thin layer of said iron over a stationary surface,

(b) establishing a vortical path of movement for said layer as it travels over said stationary surface, whereby a vortex is formed,

(c) introducing an oxidizing gas into said layer as it travels said vortical path, and

(d) removing the molten iron from the center of the vortex.

2. The process of claim 1 wherein said stationary surface is the interior surface of a vertically-orientated, coneshape vessel with an opening in the apex at the bottom thereof, and said molten iron is introduced trangentially against the upper interior surface of said vessel so that said molten metal layer travels down throguh said vessel along said vortical path.

3. The process of claim 2 in which said molten iron is the product of a blast furnace.

4. The process of claim 2 in which said molten iron has a high silicon content.

References Cited by the Examiner UNITED STATES PATENTS 11/1936 Clamer 7561 10/1958 Von Bogdandy 75-60 12/1958 Eketorp et a1 7560 12/ 1962 Churcher 26634 FOREIGN PATENTS 2/1940 Austria. 1/ 1942 Great Britain.

BENJAMIN HENKIN, Primary Examiner. 

1. A PROCESS FOR PREREFINING MOLTEN IRON COMPRISING: (A) PASSING A THIN LAYER OF SAID IRON OVER A STATIONARY SURFACE, (B) ESTABLISHING A VORTICAL PATH OF MOVEMENT FOR SAID LAYER AS IT TRAVELS OVER SAID STATIONARY SURFACE, WHEREBY A VORTEX IS FORMED, (C) INTRODUCING AN OXIDIZED GAS INTO SAID LAYER AS IT TRAVELS SAID VORTICAL PATH, AND (D) REMOVING THE MOLTEN IRON FROM THE CENTER OF THE VORTEX. 